But in this case, it’s an increase because you have lost income…ie. investing the money in a one year CD, 2 year CD, 3 year CD - so when they mature, you’ve made money).
In this case, Skidmore is just investing the money at a return or using it instead of borrowing - thus saving interest.
The person paying the four years up front has lost income although that income may have been lost due to an annual increase - so yes, the price is the same, but it really isn’t. Skidmore is making money on overpaid receivables - and each year, they remove 25% of that receivable.